A Big thank you to the uploader on this.
Loads of knockabout action, with Cap saving the day' almost every episode.
I downloaded the mp4, quality is very good.

What really distinguishes this serial from all the others I've seen here at IA is all the death. People are killed in almost every episode, with glory hound Captain America just as bloodthirsty as the evil mastermind, The Scarab. Otherwise, this is a fairly typical gangster-style serial: Each episode ends in a cliffhanger; when a gun is drawn it almost always means there will be a brawl; both sides have blinders on while trying to find out each other's real identity; the battle goes back and forth, with the edge inexorably going to good guys, till the end.
The acting is decent enough. I always enjoy Lionel Atwill. The stuntmen sometimes really overdo it. You'll begin to recognize a certain hallway with elevators. It gets around. Fifteen episodes seem too many.
I downloaded the MPEG4 files. Video and audio were fine.